This invention relates to a retractable covering, particularly a covering for an architectural opening, such as a window or a door blind or shade.
Conventional, blinds and shades for windows and doors include a head rail, a bottom rail, one or more window covering elements extending between the head rail and the bottom rail, at least two lift cords extending from the head rail and supporting the bottom rail, and a mechanism to limit the downward movement or drop of the bottom rail.
For pleated or roman shades, the drop height of the shades has usually been limited by a cord connector, engaging the cord outlet at the bottom of the head rail upon full drop of the bottom rail. Sometimes pleated and roman shades have also been provided with an additional cord to limit drop. On the other hand, for venetian blinds the full drop has usually been limited by the full extension of the lift cords.
Limiting drop without additional cords by making use of the lift cord has presented obvious advantages because fewer elements are used in assembling the blinds or shades.
Experience has shown, however, that providing the proper lengths of the lift cords between the head rail and the bottom rail for controlling drop has not been easy.
Conventional shades have had a minimum of two lift cords co-extending through the shade members and holding the bottom rail at several locations based along its length. The free ends of these lift cords have extended through the head rail to an exit opening or cord lock in one of its longitudinal ends, and the free ends have optionally been joined or knotted together in a cord connector outside the head rail.
Accurate adjustment of drop is important because the bottom rail should not hit the windowsill or floor nor should it be suspended too high so that an unsightly gap exists between the bottom rail and the windowsill or floor. However, it is not easy to precisely set the drop by adjusting the final location of a knot along the lift cords, at least prior to making the knot.
Our European patent EP 0 892 144 describes an adjuster which is connected to the lower end of the lift cords and which allows for fine adjustment of the maximum drop height of the bottom rail. This adjuster allows all the lift cords which are connected to it to be adjusted simultaneously. The adjuster can be readily operated by an end user and thereby allows the maximum drop height of the bottom rail to be adjusted after installation without the need for calling out a professional installer. The disclosure of EP 0 892 144 is incorporated herein in its entirety.